The present invention relates to photo detection devices, more particularly to avalanche photo diodes and a producing method therefor.
There are related arts as follows.
In Shingakugihou, OQE86- 183, pp. 71-78, discussed is a device including a ring-like guardring junction doped with an impurity and having a comparatively low concentration distribution and a main junction composed of comparatively high concentration impurity.
In JP-A-Sho-61-136225, disclosed is a device having a ring-like guardring junction in which the impurity concentration is comparatively low in the vicinity of a pn-junction, while high in the outer side surface.
In JP-A-Sho-61-51674, disclosed is a device in which a guardring junction is provied in the circumferential portion of a main junction having a depth which varies depending on places.
In JP-A-Hei-2-159775, disclosed is a device in which a guardring junction is provided in the circumference of a main junction having a depth which is deep at the central portion and shallow in the circumferential portion.